The invention relates to an engine power boost control system.
Utility vehicles, such as agricultural tractors have been designed in recent years to run at higher road speeds in response to customer demands for reduced hauling times and quicker delivery of tractors to the field for work. To make the tractor more suitable for these higher speeds, manufacturers have introduced new suspension systems, brakes, and steering systems. A further consideration is the increased engine power demanded to navigate hills at higher speeds for a given tractor size. Typical methods for increasing engine power involve larger and more expensive engines, cooling systems, mufflers, air cleaners, and hood enclosures. These methods for achieving power are costly and may compromise important features of the tractor, such as visibility from the operator""s seat to the field rows, above and on either side of the engine enclosure, and maintaining a compact turning radius. For this reason, manufacturers are inclined to offer higher speed options without an engine power increase. Nonetheless, customers desire that the engine power should be commensurate with the higher transport speed, and that when road loads are encountered in cases such as hill climbing, that the tractor should maintain a higher speed than a previous, slower speed tractor. Thus, there is a need for an engine power boost operable in connection with higher transport speeds.
An engine power boost system for a combine which boosts engine power when the grain auger is engaged is described in U.S. Pat. No. 4,522,553 issued in 1985 and assigned to the assignee of this application. Power boost has also been used to assist hydrostatic steering efforts in the John Deere 9000 Series rubber-tracked tractor, such as described in U.S. Pat. No. 6,138,782 issued Oct. 31, 2000 and assigned to the assignee of this application (Attorney""s Docket No. 14746-US). Construction equipment, such as the John Deere 772CH Grader, have employed multiple engine power curves as a function of gear and whether or not front wheel drive is selected.
Since 1989, John Deere 9000 series production combines have included a power boost control system which includes an ON timer and an OFF timer to control the on time and off time of power boost operation. A similar power boost control function is described in U.S. Pat. No. 5,715,790, filed on Oct. 22, 1996 and issued Feb. 10, 1998 to Tolley et al. The ""790 patent describes an engine power boost control system with a pair of timers to control the on time and off time of power boost operation of a compression-ignition engine which is normally controlled to run at throttle-selected constant engine speed up to a normal or rated engine speed. The system described by the ""790 patent is responsive to a manually operated output demand control and sensed engine speed, is enabled in response to a manually operated power boost demand control, and appears to be primarily intended for use during a plowing operation of an agricultural tractor.
Automotive and truck cruise control systems are well known, but such systems are not used with engines which are governor controlled to operate at a rated engine speed.
However, none of these systems provides a power boost function designed specifically to function in connection with higher vehicle transport or road speeds of an agricultural tractor with an engine which is governor controlled to run at a constant throttle-selected engine speed up to a normal or rated engine speed. Also, none of these systems provides a power boost system which is responsive to sensed parameters, such as transmission gear ratio, commanded or sensed vehicle speed, or various engine-related sensed temperatures. Thus, there remains a need for an engine power boost system designed specifically for an agricultural tractor operating at transport speeds. And, there remains a need for an engine power boost system which is responsive to various sensed parameters.
Accordingly, an object of this invention is to provide an engine power boost system designed for an agricultural tractor operating at transport speeds.
A further object of the invention is to provide such an engine power boost system for an agricultural tractor with an engine which is normally governor controlled to run at throttle-selected constant engine speed up to a normal or rated engine speed.
Another object of the invention is to provide such an engine power boost system which is responsive to sensed parameters, such as transmission gear ratio, commanded or sensed vehicle speed, and/or various sensed engine-related temperatures
These and other objects are achieved by the present invention, wherein a power boost control system is provided for a compression-ignition engine which is normally governor controlled to run at throttle-selected constant engine speed up to a normal or rated engine speed. The power boost control system receives a road speed signal, and power boost is disabled upon startup. Power boost is enabled if sensed road speed is greater than a first or xe2x80x9conxe2x80x9d threshold, above which is considered to be a transport speed. Power boost is disabled if sensed road speed is less than a second or xe2x80x9coffxe2x80x9d threshold, below which is considered to be less than a transport speed. When power boost is enabled, the engine governor will increase engine power levels to above normal levels, so that, for example, the desired road or transport speed can be maintained as the vehicle goes up a hill. The xe2x80x9conxe2x80x9d threshold is preferably greater than the xe2x80x9cofxe2x80x9d threshold to prevent the system from xe2x80x9chuntingxe2x80x9d or constantly enabling and disabling power boost. Different amounts of power boost can be enabled and disabled as a function of different pairs of xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d thresholds. In alternative embodiments of the invention, engine power boost may be controlled as function of sensed or calculated transmission gear ratio and/or of various sensed temperatures associated with the engine.